Two points, please.
1. The Merchant Marine crews suffered a per capita casualty rate greater than those of the U.S. Armed Forces. Let that sink in for a minute. This article notes that their percentage losses were even higher than the Marine Corps. It’s a good read.
https://www.wearethemighty.com/history/merchant-marine-worst-losses-wwii?rebelltitem=5#rebelltitem5
2. I don’t doubt the story your USN vet friend told you. But there are also stories of Army infantry guys who spent the whole war sleeping in some depot in Alabama. So anecdotal stories often don’t tell the whole picture.
By the way, I don’t know anyone personally who was in the WW II Merchant Marine. So I’m not defending anyone I know. But I have read about their service, and I am by and large impressed. It took a bit of courage to voluntarily climb aboard a merchant ship headed for the Atlantic, especially in 1941 and 1942.
So I will give credit were credit is due.
My father had a classmate in engineering school, post-WW2, who thought he could avoid the draft in 1941 by joining the Merchant Marine.
He was assigned to the Port Arthur-Murmansk run...on an aviation gasoline tanker.